High efficiency sol-gel gas chromatography column

ABSTRACT

A capillary column ( 10 ) includes a tube structure having inner walls ( 14 ) and a sol-gel substrate ( 16 ) coated on a portion of inner walls ( 14 ) to form a stationary phase coating ( 18 ) on inner walls ( 14 ). The sol solution used to prepare the sol-gel substrate ( 16 ) has at least one baseline stabilizing reagent and at least one surface deactivation reagent resulting in the sol-gel substrate ( 16 ) having at least one baseline stabilizing reagent residual and at least one surface deactivating reagent residual. A method of making the sol-gel solution is by mixing suitable sol-gel precursors to form the solution, stablizing the solution by adding at least one baseline stabilization reagent, deactivating the solution by adding at least one surface deactivation reagent to the solution, and reacting the solution in the presence of at least one catalyst.

BACKGROUND OF THE INVENTION

[0001] 1. Technical Field

[0002] The present invention relates to analytical separation technologyand more specifically towards gas chromatography separation systemsbased on sol-gel stationary phases having improved performancecharacteristics.

[0003] 2. Background Art

[0004] The introduction of an open tubular column by Golay (Golay, M. J.E., et al.,) about three decades ago, has revolutionized the analyticalcapability of gas chromatography (hereinafter “GC”). More specifically,capillary GC has matured into a separation technique that is widely usedin various fields of science and industry (Altgelt, K. H., et al.;Clement, R. E.; Berezkin, V. G., et al.; and Tebbett, I.). Capillary GCis a separation technique in which the vapor phase of a sample in agaseous, mobile phase passes through a capillary tube whose inner wallscontain a thin film of an adsorbing or absorbing medium (i.e.,stationary phase). Because of differential interactions of the samplecomponents with the stationary phase, the individual components of thesample move through the column with different velocities. This leads tothe physical separation of the sample components into individualchromatographic zones as they move down the column with theircharacteristic velocities. The separated components are detectedinstrumentally as they are eluted from the column. Contemporarytechnology for the preparation of open tubular columns istime-consuming. It consists of three major, individually executed steps(Poole, C. F., et al.): capillary surface deactivation (Woolley, C. L.et al.), static coating (Bouche, J. et al.), and stationary phaseimmobilization (Blomberg L. G.). Involvement of multiple steps inconventional column technology increases the fabrication time and islikely to result in greater column-to-column variation. The columndeactivation step is critically important for the GC separation of polarcompounds that are prone to undergo adsorptive interactions (e.g., withthe silanol groups on fused silica capillary inner walls). Inconventional column technology, deactivation is usually carried out as aseparate step, and involves chemical derivatization of the surfacesilanol groups. Various reagents have been used to chemically deactivatethe surface silanol groups (de Nijs; R. C. M., et al.; Schomburg, G. etal.; Blomberg, L. et al.; and Lee, M. L. et al.). Effectiveness of thesedeactivation procedures greatly depends on the chemical structure andcomposition of the fused silica surface to which they are applied.

[0005] Of special importance are the concentration and mode ofdistribution of surface silanol groups. Because the fused silicacapillary drawing process involves the use of high temperatures (˜2,000°C.), the silanol group concentration on the drawn capillary surface caninitially be low due to the formation of siloxane bridges underhigh-temperature drawing conditions. During subsequent storage andhandling, some of these siloxane bridges can undergo hydrolysis due toreaction with environmental moisture. Thus, depending on thepost-drawing history, even the same batch of fused silica capillary canhave different concentrations of the silanol groups that can also varyby the modes of their distribution on the surface.

[0006] Moreover, different degrees of reaction and adsorption activitiesare shown by different types of surface silanol groups (Lawrocki, J.).As a result, fused silica capillaries from different batches or evenfrom the same batch but stored and/or handled under differentconditions, cannot produce identical surface characteristics after beingsubjected to the same deactivation treatments. This makes surfacedeactivation a difficult procedure to reproduce. To overcome thesedifficulties, some researchers have used hydrothermal surface treatmentsto standardize silanol group concentrations and their distributions overthe surface (Sumpter, S. R. et al.). This additional step however, makesthe time consuming column making procedure even longer. Static coatingis another time-consuming step in conventional column technology. Atypical 30-m long column can require as much as ten hours or more forstatic coating. The duration of this step can vary depending on thelength and diameter of the capillary, and the volatility of the solventused.

[0007] To coat a column by the static coating technique, the fusedsilica capillary is filled with a stationary phase solution prepared ina low-boiling solvent. One end of the capillary is sealed using a highviscosity grease or by some other means (Abe, I. et al.), and the otherend is connected to a vacuum pump. Under these conditions, the solventbegins to evaporate from the capillary end connected to the vacuum pump,leaving behind the stationary phase that becomes deposited on thecapillary inner walls as a thin film. Stationary phase film of desiredthickness could be obtained by using a coating solution of appropriateconcentration that can be easily calculated through simple equations(Ettre, L. S. et al.).

[0008] In static coating, two major drawbacks are encountered. First,the technique is excessively time consuming, and not very suitable forautomation. Second, the physically coated stationary phase film shows apronounced tendency to rearrangements that can ultimately result indroplet formation due to Rayleigh instability (Bartle, K. D. et al.).Such a structural change in the coated films can serve as a cause forthe deterioration or even complete loss of the column's separationcapability.

[0009] To avoid these undesirable effects, static-coated stationaryphase films need to be stabilized immediately after their coating. Thisis usually achieved by stationary phase immobilization through freeradical cross-linking (Wright, B. W. et al.) that leads to the formationof chemical bridges between coated polymeric molecules of the stationaryphase. In such an approach, stability of the coated film is achieved notthrough chemical bonding of the stationary phase molecules to thecapillary walls, but mainly through an increase of their molecular sizeand consequently, through decrease of their solubility and vaporpressure.

[0010] Such an immobilization process has a number of drawbacks. First,polar stationary phases are difficult to immobilize by this technique(Yakabe, Y., et al.). Second, free radical cross-linking reactions aredifficult to control to ensure the same degree of cross-linking indifferent columns with the same stationary phase. Third, cross-linkingreactions can lead to significant changes in the polymer structure andchromatographic properties of the resulting immobilized polymer cansignificantly differ from those of the originally taken stationary phase(Blomberg L. G.). All these drawbacks add up to make column preparationby conventional techniques a task that is difficult to control andreproduce (Blomberg, L., et al.).

[0011] In order to overcome all of the above problems, a preparation ofa GC capillary column including a tube structure and a deactivatedsurface-bonded sol-gel coating on a portion of the tube structureforming a stationary phase was disclosed and claimed in PCT ApplicationPCT/US99/19113, published as WO 00/11463, to Malik et al. The inventiondisclosed therein is for a structure for forming a capillary tube, e.g.,for gas chromatography, and a technique for forming such capillary tube.The capillary tube includes a tube structure and a deactivatedsurface-bonded sol-gel coating on a portion of the tube structure toform a stationary phase coating on that portion of the tube structure.The deactivated sol-gel stationary phase coating enables separation ofanalytes while minimizing adsorption of analytes on the separationcolumn structure. This type of column was a significant advancement inthe art, but it was recognized that certain improvements would greatlyenhance the performance of the sol-gel coated column.

[0012] One area of improvement deals with baseline stability. A GCcolumn is commonly operated under temperature-programmed conditionswhereby the temperature of the column is increased with time. As thecolumn temperature increases, the gas chromatography baseline risesbecause of column bleed caused due to the formation of volatilecompounds from the stationary phase coating on the inner surface of thecapillary column. In GC columns with polyslioxane-based stationaryphases, the formation of volatile cyclic compounds is favored by theflexibility of the polysiloxane chains. One way to overcome orsignificantly reduce the column-bleeding problem is to reduce theflexibility of the polymeric structure of the GC stationary phase byincorporating phenyl rings in the polysiloxane backbone. This reducesthe flexibility of polysiloxanes, and consequently, their ability toproduce cyclic volatiles through rearrangements. The selection of thephenyl-containing reagent and the degree of substitution in thepolysiloxane backbone are both critical, and care must be taken so thatthe stationary phase does not become too rigid. Otherwise,chromatographic properties of the polymer (especially the mass transferproperties) can be compromised. In an attempt to provide increasedbaseline stability, Mayer et al. used1,4-bis(hydroxydimethylsilyl)benzene to incorporate a phenyl ring in thepolydimethyldiphenylsiloxane structure by conducting its reaction withdiphenylsilanediol at 110° C. for 48 hours. This non-sol-gel processhowever, is inconvenient for two reasons. First, the process is lengthyand carried out at elevated temperature. Second, the1,4-bis(hydroxydimethylsiyl)benzene reagent used for the incorporationof the phenyl group provides a polymer structure where the phenyl ringis directly bonded to silicon atoms without any spacer groups and leadsto a very rigid polymer affecting its mass transfer properties andchromatographic efficiency.

[0013] Accordingly, there is a need for an improved GC column havingimproved baseline stability, higher efficiency, and reduced conditioningtime. Additionally, there is a need for a sol-gel GC column havingdesired stationary phase film thickness and improved retentioncharacteristics that are capable of being fabricated into long columns.The present invention describes a sol-gel chemistry-based process thatprovides all of the above-mentioned desirable column characteristicsthrough a simple procedure carried out under mild thermal conditions.

SUMMARY OF THE INVENTION

[0014] According to the present invention, there is provided a capillarycolumn including a tube structure having inner walls and a sol-gelsubstrate coated on a portion of the inner walls of the tube structureto form a stationary phase coating on the inner walls. The sol solutionused to prepare the sol-gel substrate has at least one baselinestabilizing reagent and at least one surface deactivation reagent. Theresulting sol-gel substrate has at least one baseline stabilizingreagent residual and at least one surface deactivation reagent residual.The present invention further provides for a method of making a sol-gelsolution for placement into a capillary column by mixing suitablesol-gel precursors, at least one sol-gel-active organic polymer orligand, at least one baseline stabilization reagent to the sol-gelsolution, at least one surface deactivation reagent, and at least onesol-gel catalyst.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Other advantages of the present invention are readily appreciatedas the same becomes better understood by reference to the followingdetailed description when considered in connection with the accompanyingdrawings wherein:

[0016]FIG. 1 is a longitudinal, cross-sectional view of an embodiment ofa capillary column of the present invention;

[0017]FIG. 2 is drawing of an embodiment of the present invention, morespecifically, a filling and purging device for the preparation of thecapillary column of the present invention;

[0018]FIG. 3A. GC separation of Grob test mixture on a sol-gel-coatedPDMS column prepared using a sol solution containing hydroxy-terminatedpolydimethylsiloxane, poly dimethyl (82-86%) diphenyl (14-18%) siloxane,hydroxy-terminated poly(methylhydrosiloxane), methyltrimethoxysilane,1,1,1,3,3,3,-hexamethyldisilazane, trifluoroacetic acid, andbis(trimethoxysilylethyl)benzene, but no ammonium fluoride, wherein theconditions are: 10-m×250-μm-i.d. fused silica capillary column;stationary phase, sol-gel PDMS; carrier gas, helium; injection, split(100:1, 300° C.); detector, FID, 350° C.; temperature programming from40° C. at 6° C. minutes⁻¹ with peaks (1) 2,3-butanediol, (2) n-decane,(3) 1-octanol, (4) 1-nonanal (5) n-undecane, (6) 2,6-dimethylaniline,(7) methyl decanoate, (8) methyl undecanoate, and (9) methyldodecanoate;

[0019]FIG. 3B. GC separation of Grob test mixture on a sol-gel-coatedPDMS capillary column prepared using a sol solution containinghydroxy-terminated polydimethylsiloxane, hydroxy-terminated polydimethyl (82-86%) diphenyl (14-18%) siloxane, poly(methylhydrosiloxane),methyltrimethoxysilane, 1,1,1,3,3,3-hexamethyldisilazane,trifluoroacetic acid, and both ammonium fluoride andbis(trimethoxysilylethyl)benzene, wherein the conditions are: 10-m×250μm-i.d. fused silica capillary column; stationary phase, sol-gel PDMS;carrier gas, helium; injection, split (100:1, 300° C.); detector, FID,350° C.; temperature programming from 40° C. at 6° C. minutes⁻¹ withpeaks (1) 2,3-butanediol, (2) n-decane, (3) 1-octanol, (4)2,6-dimethylphenol, (5) 1-nonanal, (6) n-undecane, (7)2,6-dimethylaniline (8) methyl decanoate, (9) dicyclohexylamine, (10)methyl undecanoate and (11) methyl dodecanoate;

[0020]FIG. 4A. GC separation of Grob test mixture on a sol-gel-coatedPDMS capillary column prepared using a sol solution containinghydroxy-terminated polydimethylsiloxane, hydroxy-terminated polydimethyl (82-86%) diphenyl (14-18%) siloxane, poly(methylhydrosiloxane),methyltrimethoxysilane, 1,1,1,3,3,3-hexamethyldisilazane,trifluoroacetic acid, ammonium fluoride but nobis(trimethoxysilylethyl)benzene, wherein the conditions are:10-m×250-μm-i.d. fused silica capillary column; stationary phase,sol-gel PDMS; carrier gas, helium; injection, split (100:1, 300° C.);detector, FID, 350° C.; temperature programming from 40° C. at 6° C.minutes⁻¹and with peaks (1) 2,3-butanediol, (2) n-decane, (3) 1-octanol,(4) 2,6-dimethylphenol, (5) 1-nonanal, (6) n-undecane, (7)2,6-dimethylaniline (8) methyl decanoate, (9) dicyclohexylamine, (10)methyl undecanoate, and (11) methyl dodecanoate;

[0021]FIG. 4B is a GC separation of Grob test mixture on asol-gel-coated PDMS capillary column prepared using a sol solutioncontaining hydroxy-terminated polydimethylsiloxane, hydroxy-terminatedpoly dimethyl (82-86%) diphenyl (14-18%) siloxane,poly(methylhydrosiloxane), methyltrimethoxysilane,1,1,1,3,3,3-hexamethyldisilazane, trifluoroacetic acid, ammoniumfluoride, and bis(trimethoxysilylethyl)benzene with conditions being10-m×250-μm-i.d. fused silica capillary column; stationary phase,sol-gel PDMS; carrier gas, helium; injection, split (100:1, 300° C.);detector, FID, 350° C.; temperature programming from 40° C. at 6° C.minutes⁻¹; and with peaks (1) 2,3-butanediol, (2) n-decane, (3)1-octanol, (4) 2,6-dimethylphenol, (5) 1-nonanal, (6) n-undecane, (7)2,6-dimethylaniline, (8) methyl decanoate, (9) dicyclohexylamine, (10)methyl undecanoate, and (11) methyl dodecanoate;

[0022]FIG. 5A is a GC separation of Grob test mixture on asol-gel-coated PDMS capillary column prepared using a sol solutioncontaining hydroxy-terminated polydimethylsiloxane, hydroxy-terminatedpoly dimethyl (82-86%) diphenyl (14-18%) siloxane,poly(methylhydrosiloxane), methyltrimethoxysilane, trifluoroacetic acid,ammonium fluoride and bis(trimethoxysilylethyl)benzene and1,1,1,3,3,3-hexamethyldisilazane, with conditions being 10-m×250-μm-i.d.fused silica capillary column; stationary phase, sol-gel PDMS; carriergas, helium; injection, split (100:1, 300° C.); detector, FID, 350° C.;temperature programming from 40° C. at 6° C. minutes⁻¹, and with peaks(1) 2,3-butanediol, (2) n-decane, (3) 1-octanol, (4) 2,6-dimethylphenol,(5) 1-nonanal, (6) n-undecane, (7) 2,6-dimethylaniline, (8) methyldecanoate, (9) dicyclohexylamine, (10) methyl undecanoate, and (11)methyl dodecanoate;

[0023]FIG. 5B is a GC separation of Grob test mixture on asol-gel-coated PDMS capillary column prepared using a sol solutioncontaining hydroxy-terminated polydimethylsiloxane, hydroxy-terminatedpoly dimethyl (82-86%) diphenyl (14-18%) siloxane,poly(methylhydrosiloxane), methyltrimthoxysilane, trifluoroacetic acid,ammonium fluoride and bis(trimethoxysilylethyl)benzene but no1,1,1,3,3,3-hexamethyldisilazane, with conditions being 10-m×250-μm-i.d.fused silica capillary column; stationary phase, sol-gel PDMS; carriergas, helium; injection, split (100:1, 300° C.); detector, FID, 350° C.;temperature programming from 40° C. at 6° C. minutes⁻¹ and peaks (1)2,3-butanediol, (2) n-decane, (3) 1-octanol, (4) 2,6-dimethylphenol, (5)n-undecane, (6) 2,6-dimethylaniline, (7) methyl decanoate, (8) methylundecanoate, and (9) methyl dodecanoate;

[0024]FIG. 6 is a GC separation of Grob test mixture on a sol-gel-coatedPDMS capillary column prepared using a sol solution containinghydroxy-terminated polydimethylsiloxane, hydroxy-terminated polydimethyl (82-86%) diphenyl (14-18%) siloxane, poly(methylhydrosiloxane),methyltrimethoxysilane, 1,1,1,3,3,3-hexamethyldisilazane,trifluoroacetic acid, ammonium fluoride andbis(trimethoxsilylethyl)benzene, with conditions being 10-m×250-μm-i.d.fused silica capillary column; stationary phase, sol-gel PDMS; carriergas, helium; injection, split (100:1, 300° C.); detector, FID, 350° C.;temperature programming from 40° C. at 6° C. minutes⁻¹; and with peaks(1) 2,3-butanediol, (2) n-decane, (3) 1-octanol, (4) 2,6-dimethylphenol,(5) 1-nonanal, (6) n-undecane, (7) 2,6-dimethylaniline, (8) methyldecanoate, (9) dicyclohexylamine, (10) methyl undecanoate, and (11)methyl dodecanoate;

[0025]FIG. 7 is a GC separation of PAHs on a sol-gel-coated PDMScapillary column prepared using a sol solution containinghydroxy-terminated polydimethylsiloxane, hydroxy-terminated polydimethyl (82-86%) diphenyl (14-18%) siloxane, poly(methylhydrosiloxane),methyltrimethoxysilane, 1,1,1,3,3,3-hexamethyldisilazane,trifluoroacetic acid, ammonium fluoride andbis(trimethoxysilylethyl)benzene with conditions being 10-m×250-μm-i.d.fused silica capillary column; stationary phase, sol-gel PDMS; carriergas, helium; injection, split (100:1, 300° C.); detector, FID, 350° C.,temperature programming from 80° C. at 6° C. minutes⁻¹ and with peaks(1) naphthalene, (2) acenaphthylene, (3) acenaphthene, (4) fluorene, (5)phenanthrene, (6) o-terphenyl, (7) fluoranthene, and (8) pyrene;

[0026]FIG. 8 is a GC separation of aniline derivatives on asol-gel-coated PDMS capillary column prepared using a sol solutioncontaining hydroxy-terminated polydimethylsiloxane, hydroxy-terminatedpoly dimethyl (82-86%) diphenyl (14-18%) siloxane,poly(methylhydrosiloxane), methyltrimethoxysilane,1,1,1,3,3,3-hexamethyldisilazane, trifluoroacetic acid, ammoniumfluoride and bis(trimethoxysilylethyl)benzene, with conditions being10-m×250-μm-i.d. fused silica capillary column; stationary phase,sol-gel PDMS; carrier gas, helium; injection, split (100:1, 300° C.);detector, FID, 350° C.; temperature programming from 40° C. at 6° C.minutes⁻¹ and with peaks (1) pyridine, (2) N-methylaniline, (3)2-ethylaniline, (4) 4-ethylaniline, (5) N-butylaniline;

[0027]FIG. 9 is a gas chromatogram demonstrating separation of a Grobtest mixture on a sol-gel-coated PEG column, wherein the conditions are:10-m×250-μm-i.d. fused silica capillary column; stationary phase,sol-gel polyethylene glycol (PEG); carrier gas, helium; injection, split(100:1, 300° C.); detector, FID, 350° C., temperature programming from40° C. at 6° C. min⁻¹; and with peaks (1) n-decane, (2) n-undecane, (3)nonanal, (4) 2,3-butanediol, (5) 1-octane, (6) methyl decanoate, (7)dicylcohexylamine, (8) methyl undecanoate, (9) methyl dodecanoate, (10)2,6-dimethylaniline, (11) 2,6-dimethylphenol, and (12) 2-ethylhexanoicacid;

[0028]FIG. 10 is a gas chromatogram illustrating separation of anilinederivatives on a sol-gel coated PEG column, wherein the conditions are:10-m×250-μm-i.d. fused silica capillary column; stationary phase,sol-gel polyethylene glycol (PEG); carrier gas, helium; injection, split(100:1, 300° C.); detector, FID, 350° C.; temperature programming from65° C. at 6° C. min⁻¹; and with peaks (1) N,N-dimethylaniline, (2)N-methylaniline, (3) N-ethylaniline, (4) 2-ethylaniline, (5)4-ethylaniline, and (6) 3-ethylaniline;

[0029]FIG. 11 is a gas chromatogram illustrating separation of aldehydeson a sol-gel coated PEG column, wherein the conditions are: 10-m×250μm-i.d. fused silica capillary column; stationary phase, sol-gelpolyethylene glycol (PEG); carrier gas, helium; injection, split (100:1,300° C.); detector, FID, 350° C.; temperature programming from 75° C. at6° C. min⁻¹; and with peaks (1) nonylaldehyde, (2) benzaldehyde, (3)o-toulaldehyde, (4) m-toulaldehyde, and (5) p-toulaldehyde;

[0030]FIG. 12 is a gas chromatogram demonstrating separation of ketoneson a sol-gel coated PEG column, wherein the conditions are:10-m×250-βm-i.d. fused silica capillary column; stationary phase,sol-gel polyethylene glycol (PEG); carrier gas, helium; injection, split(100:1, 300° C.); detector, FID, 350° C.; temperature programming from80° C. at 6° C. min⁻¹; and with peaks (1) 5-nonanone, (2) butyrophenone,(3) valerophenone, (4) hexanophenone, and (5) heptanophenone;

[0031]FIG. 13 is a gas chromatogram illustrating separation of alcoholson a sol-gel coated PEG column, wherein the conditions are: 10-m×250μm-i.d. fused silica capillary column; stationary phase, sol-gelpolyethylene glycol (PEG); carrier gas, helium; injection, split (100:1,300° C.); detector, FID, 350° C.; temperature programming from 70° C. at6° C. min⁻¹; and with peaks (1) butanol, (2) pentanol, (3) hexanol, (4)heptanol, and (5) octanol;

[0032]FIG. 14 is a schematic illustration of hydrolysis reactionsinvolved in the preparation of sol-gel PDMS coated columns according tothe present invention;

[0033]FIG. 15 is a schematic illustration of condensation reactionsinvolved in sol-gel PDMS stationary phase of the present invention;

[0034]FIG. 16 is a schematic illustration of a condensation reaction ofthe present invention occurring on a fused silica capillary innersurface;

[0035]FIG. 17 is a schematic illustration of a deactivation of residualsilanol groups using hexamethyldisilazane (HMDS);

[0036]FIG. 18 is a schematic illustration of hydrolysis reactions forthe preparations of sol-gel PEG coated columns according to the presentinvention;

[0037]FIG. 19 is a schematic illustration of a condensation reaction ofthe present invention demonstrating the growth of a sol-gel PEG polymer(A is a spacer group);

[0038]FIG. 20 is a schematic illustration of a growing sol-gel PEGpolymer being bonded to a silica surface;

[0039]FIG. 21 is a schematic illustration of a reaction of the sol-gelPEG polymer bonded to a silica surface with hexamethyldisilazane (HMDS)to form a deactivated sol-gel PEG polymer coating bonded to the silicasurface;

[0040]FIG. 22A is a scanning electron micrograph of a sol-gel PDMScoating on the inner surface of a fused silica capillary column(magnification 10,000×); and

[0041]FIG. 22B is a scanning electron micrograph of a sol-gel PEGcoating on the inner surface of a fused silica capillary column(magnification 10,000×).

DETAILED DESCRIPTION OF THE INVENTION

[0042] Generally, the present invention is directed to a capillarycolumn and to a method of making the capillary column, wherein thecapillary column provides for a rapid and simple method for simultaneousdeactivation, coating, and stationary phase immobilization in gaschromatography (hereinafter “GC”). To achieve this goal, a sol-gelchemistry-based approach to column preparation is provided that is aviable alternative to conventional GC column technology. The sol-gelcolumn technology eliminates the major drawbacks of conventional columntechnology through chemical bonding of the sol-gel stationary phasemolecules to an interfacial layer that evolves on the top of theoriginal capillary surface. More specifically, the present inventionprovides for a sol-gel GC column having improved baseline stability,higher efficiency, and reduced conditioning time. The present inventionfurther provides for a sol-gel GC column having desired stationary phasefilm thicknesses and improved retention characteristics that are capableof being fabricated into long columns as long as 30 meters or longer.The present invention is useful for capillary systems as well as anyother chromatography system that employs the use of polysiloxane-based,PEG-based, and other types of stationary phases for separation.

[0043] The term “baseline stability” as used herein is defined as, butis not limited to, a state wherein the formation of volatile productsdue to the breakdown of the stationary phase at elevated temperatures ishindered or prevented. More specifically, baseline stability occurs whenthe stationary phase is prevented from rearrangement so that theformation of low molecular weight compounds is suppressed. This can beachieved through a reduction of polymer chain flexibility by introducinga rigid phenyl group into the polymer backbone.

[0044] The term “deactivation reagent” as used herein is defined as, butis not limited to, any reagent that reacts with the polar adsorptivesites (e.g., silanol groups) on the column inner surface or stationaryphase coating, and thereby prevents the stationary phase coating withinthe column from adsorbing polar analytes. The adsorptive interaction ofthe stationary phase with polar analytes occurs because of the presenceof silanol groups that are harmful to polar compounds desired to beanalyzed.

[0045] The present invention has numerous applications and uses.Primarily, the present invention is useful in separation processesinvolving analytes including, but not limited, to hyrdocarbons,polycyclic aromatic hydrocarbons (PAHs), alcohols, aldehydes, ketones,phenols, fatty acids, fatty acid methyl esters, amines, and otheranalytes known to those of skill in the art. Accordingly, the presentinvention is useful in chemical, petrochemical, environmental,pharmaceutical applications, and other similar applications.

[0046] The present invention has various advantages over the prior art.The sol-gel chemistry-based novel approach to column technology ispresented for high resolution capillary GC that provides a fast way ofsurface roughening, deactivation, coating, and stationary phaseimmobilization—all carried out in a single step. Unlike conventionalcolumn technology in which these procedures are carried out asindividual, time-consuming, steps, the new technology can achieve allthese just by filling a capillary with a sol solution of appropriatecomposition, and allowing it to stay inside the capillary for acontrolled period, followed by inert gas purging and conditioning of thecapillary. The new technology greatly simplifies the methodology for thepreparation of high efficiency GC columns, and offers an opportunity toreduce the column preparation time at least by a factor of ten. Beingsimple in technical execution, the new technology is very suitable forautomation and mass production. Columns prepared by the new technologyprovide significantly superior thermal stability due to direct chemicalbonding of the stationary phase coating to the capillary walls. Enhancedsurface area of the columns, as evidenced by SEM results, provides asample-capacity advantage to the sol-gel columns. The new methodologyprovides excellent surface deactivation quality, which is eithercomparable with or superior to that obtained by conventional techniques.This is supported by examples of high efficiency separations obtainedfor polar compounds including free fatty acids, amines, alcohols, diols,phenols, aldehydes and ketones. The sol-gel column technology has thepotential to offer a viable alternative to existing methods for columnpreparation in analytical microseparation techniques.

[0047] The present invention has numerous embodiments, depending uponthe desired application. As described below, the formation of thevarious embodiments are intended for use in gas chromatography. However,due to the vast applicability of the present invention, the column andrelated methods thereof can be modified in various manners for use inother areas of analytical separation technologies. The principles of thepresent invention can also be used to form capillary columns for use inliquid chromatography, capillary electrochromatography, supercriticalfluid chromatography, and as sample preconcentrators where a compound ofinterest is present in very small concentrations in a sample.

[0048] In one embodiment (FIG. 1), the present invention provides for acapillary column 10 including a tube structure 12 having inner walls 14and a sol-gel substrate 16 coated on a portion of the inner walls 14 ofthe tube structure 12 to form a stationary phase coating 18 on the innerwalls 14. The stationary phase coating 18 is created using at least onebaseline stabilizing reagent and at least one surface deactivationreagent. The stationary phase coating 18 is bonded to the inner walls 14of the tube structure 12. The surface-bonded sol-gel substrate 16 isapplied to the inner walls 14 of the tube structure 12 by use of anapparatus as illustrated in FIG. 2 and the method described herein.

[0049] The tube structure 12 of the capillary column 10 can be made ofnumerous materials including, but not limited to alumina, fused silica,glass, titania, zirconia, polymeric hollow fibers, and any other similartubing materials known to those of skill in the art. Typically, fusedsilica is the most convenient material used. Sol-gel chemistry inanalytical microseparations presents a universal approach to creatingadvanced material systems including those based on alumina, titania, andzirconia that have not been adequately evaluated in conventionalseparation column technology. Thus, the sol-gel chemistry-based columntechnology has the potential to effectively utilize advanced materialproperties to fill this gap.

[0050] As for the sol-gel substrate, it has the formula:

[0051] wherein,

[0052] X=Residual of a deactivation reagent (e.g.,polymethylhydrosiloxane (PMHS), hexamethyldisilazane (HMDS), etc.);

[0053] Y=Sol-gel reaction residual of a sol-gel active organic molecule(e.g., molecules with hydroxysilane or alkoxysilane monomers,polydimethylsiloxane (PDMS), polymethylphenylsiloxane (PMPS),polydimethyldiphenylsiloxane (PDMDPS), polyethylene glycol (PEG) andrelated polymers such as Carbowax 20M, polyalkylene glycol such as Ucon,macrocyclic molecules such as cyclodextrins, crown ethers, calixarenes,alkyl moieties such as octadecyl, octyl, a residual from a baselinestabilizing agent such as bis(trimethoxysilylethyl)benzene,1,4-bis(hydroxydimethylsilyl)benzene, etc.

[0054] Z=Sol-gel precursor-forming chemical element (e.g., Si, Al, Ti,Zr, etc.)

[0055] l=An integer≧0;

[0056] m=An integer≧0;

[0057] n=An integer≧0;

[0058] p=An integer≧0;

[0059] q=An integer≧0; and

[0060] l, m, n, p, and q are not simultaneously zero.

[0061] Dotted lines indicate the continuation of the chemical structurewith X, Y, Z, or Hydrogen (H) in space.

[0062] In the preparation of gas chromatography columns, it is desirableto use sol-gel solutions to coat the walls of capillary tube structuresfor the separation of analytes. These sol-gels are prepared by standardmethods known in the art and comprise both polysiloxane andnon-polysiloxane type gels. These include, but are not limited to,polysiloxane-based gels with a wide range of substituted functionalgroups, including: methyl, phenyl, cyanoalkyl, cyanoaryl, etc. Inaddition, sol-gel polyethylene glycols such as, but not limited to, PEG,Carbowax, Superox, sol-gel alkyl, sol-gel polyalkylene oxides, such asUcon, and other sol-gels, such as sol-gel dendrimers can be modified bythe instant invention.

[0063] In order to achieve the desired sol-gels of the instantinvention, certain reagents in a reagent system were preferred for thefabrication of the gels for the columns of the present invention. Thereagent system included two sol-gel precursors, a sol-gel active polymeror ligand, a deactivation reagent, one or more solvents and one or morea catalysts. For the purposes of this invention, the precursors utilizedfor preparing the sol-gel coated GC capillary columns of the presentinvention have the general structure of:

[0064] wherein,

[0065] Z is the precursor-forming element taken from a group including,but not limited to, silicon, aluminum, titanium, zirconium, vanadium,germanium, and the like; and

[0066] R₁, R₂, R₃, and R₄ (i.e., “R-groups”) are substituent groups atleast two of which are sol-gel-active, wherein the sol-gel active groupsinclude, but are not limited to, alkoxy, hydroxy moieties, and the like.Typical sol-gel-active alkoxy groups include, but are not limited to, amethoxy group, ethoxy group, n-Propoxy group, iso-Propoxy group,n-butoxy group, iso-butoxy group, tert-butoxy group, and any otheralkoxy groups known to those of skill in the art. If there are anyremaining R-groups, they can be any non sol-gel active groups such asmethyl, octadecyl, phenyl, and the like. It is preferred however, thatthree or four of the R-groups are sol-gel active groups.

[0067] Typical non-sol-gel-active substituents of the precursor-formingelement (Z) include, but are not limited to, alkyl moieties and theirderivatives, alkenyl moieties and their derivatives, aryl moieties andtheir derivatives, arylene moieties and their derivatives, cyanoalkylmoieties and their derivatives, fluoroalkyl moieties and theirderivatives, phenyl moieties and their derivatives, cyanophenyl moietiesand their derivatives, biphenyl moiety and its derivatives,cyanobiphenyl moieties and their derivatives, dicyanobiphenyl moietiesand their derivatives, cyclodextrin moieties and their derivatives,crown ether moieties and their derivatives, cryptand moieties and theirderivatives, calixarene moieties and their derivatives, liquid crystalmoieties and their derivatives, dendrimer moieties and theirderivatives, cyclophane moieties and their derivatives, chiral moieties,polymeric moieties, and any other similar non-sol-gel active moietiesknown to those of skill in the art.

[0068] In addition to the above mentioned and preferred precursors,other precursors can be used with the present invention. Theseprecursors include, but are not limited to, a chromatographically activemoiety selected from the group of octadecyl, octyl, cyanopropyl, diol,biphenyl, and phenyl. Other representative precursors include, but arenot limited to, Tetramethoxysilane,3-(N-styrylmethyl-2-aminoethylamino)-propyltrimethoxysilanehydrochloride, N-tetradecyldimethyl(3-trimethoxysilylpropyl)ammoniumchloride, N-(3-trimethoxysilylpropyl)-N-methyl-N,N-diallylammoniumchloride, N-trimethoxysilylpropyltri-N-butylammonium bromide,N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride,Trimethoxysilylpropylthiouronium chloride,3-[2-N-benzyaminoethylaminopropyl]trimethoxysilane hydrochloride,1,4-Bis(hydroxydimethylsilyl)benzene,Bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane,1,4-bis(trimethoxysilylethyl)benzene, 2-Cyanoethyltrimethoxysilane,2-Cyanoethyltriethoxysilane, (Cyanomethylphenethyl)trimethoxysilane,(Cyanomethylphenethyl)triethoxysilane,3-Cyanopropyldimethylmethoxysilane, 3-Cyanopropyltriethoxysilane,3-Cyanopropyltrimethoxysilane, n-Octadecyltrimethoxysilane,n-Octadecyldimethylmethoxysilane, Methyl-n-Octadecyldiethoxysilane,Methyl-n-Octadecyldimethoxysilane, n-Octadecyltriethoxysilane,n-Dodecyltriethoxysilane, n-Dodecyltrimethoxysilane,n-Octyltriethyoxysilane, n-Octyltrimethoxysilane,n-Ocyidiisobutylmethoxysilane, n-Octylmethyldimethoxysilane,n-Hexyltriethoxysilane, n-isobutyltriethoxysilane,n-Propyltrimethoxysilane, Phenethyltrimethoxysilane,N-Phenylaminopropyltrimethoxysilane, Styrylethyltrimethoxysilane,3-(2,2,6,6-tetramethylpiperidine-4-oxy)-propyltriethoxysilane,N-(3-triethoxysilylpropyl)acetyl-glycinamide,(3,3,3-trifluoropropyl)trimethoxysilane,(3,3,3-trifluoropropyl)methyldimethoxysilane,3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane,3-mercaptopropyltriethoxysilane, mercaptomethylmethyldiethoxysilane,3-mercaptopropylmethyldimethoxysilane,3-mercaptopropyloctadecyldimethoxysilane,3-mercaptopropylloctyldimethoxysilane,3-mercaptopropylcyanopropyldimethoxysilane,3-mercaptopropyloctadecyldiethoxysilane, and any other similar precursorknown to those of skill in the art.

[0069] The deactivation reagents include, but is not limited to,hydrosilanes, polymethylhydrosiloxlanes, polymethylphenylhydrosiloxanes, polymethyl cyanopropyl hydrosioloxanes, and any othersimilar deactivation reagent known to those of skill in the art. Theprimary catalyst includes, but is not limited to, trifluoroacetic acid,any acid, base, fluoride, and any other similar catalyst known to thoseof skill in the art.

[0070] According to the present invention, in addition to theabove-mentioned materials, the performance of the sol gel stationaryphase is improved by the addition of at least one baseline stabilizingreagent and at least one additional surface deactivation reagent to thesol solution. The baseline-stabilizing reagent prevents rearrangement ofthe sol-gel polymeric stationary phase and formation of volatilecompounds at elevated temperature. In order to do so, thebaseline-stabilizing reagent incorporates with the phenyl ring in thepolymer backbone structure at room temperature using a sol-gel process.The baseline-stabilizing reagent includes, but is not limited to,bis(trimethoxysilylethyl)-benzene (BIS), phenyl-containing groups,cyclohexane containing groups, and any other similar sol-gel activestabilizing reagent known to those of skill in the art. In oneembodiment, the baseline-stabilizing reagent is used in conjunction withmethyltrimethoxysilane (a sol-gel percursor), and two sol-gel catalysts(trifluoroacetic acid and ammonium fluoride). First the sol-gelreactions are carried out for ten minutes using trifluoroacetic acid asthe primary catalyst. After this, a second sol-gel catalyst is used toimprove the condensation process for the sol-gel coating and its bondingwith the capillary inner surface. The second sol-gel catalyst includes,but is not limited to, ammonium fluoride, base, fluoride, and any othersimilar catalysts known to those of skill in the art. It is known thatunder acidic conditions the hydrolysis reaction proceeds faster toproduce primarily linear polymeric structure, but the polycondensationreaction remains slow. The addition of fluoride increases thepolycondensation reaction rate.

[0071] Finally, a surface derivatization reagent is added as a secondarydeactivation reagent, which includes, but is not limited to,1,1,1,3,3,3-heaxmethyldisilazane, any hydrosilane, and any other similarsurface deactivation reagents known to those of skill in the art. Thesol-gel reactions involved in the formation of the polysiloxanestructure described herein, incorporation of phenyl ring, and chemicalbonding of the polymer to the column inner walls are illustrated inFIGS. 14-21 for sol-gel PDMS and sol-gel PEG.

[0072] The preparation of the sol-gel coating includes the steps ofproviding the tube structure, providing a sol-gel solution including oneor more sol-gel precursors, an organic material with at least onesol-gel active functional group, one or more sol-gel catalysts, one ormore deactivation reagents, and a solvent system. The sol-gel solutionis then reacted with a portion of the tube (e.g., inner surface) undercontrolled conditions to produce a surface bonded sol-gel coating on theportion of the tube. The free portion of the solution is then removedfrom the tube under pressure, purged with an inert gas, and is heatedunder controlled conditions to cause the deactivation reagent to reactwith the surface bonded sol-gel coating to deactivate and to conditionthe sol-gel coated portion of the tube structure. Preferably, thesol-gel precursor includes an alkoxy compound. The organic materialincludes a monomeric or polymeric material with at least one sol-gelactive functional group. The sol-gel catalyst is taken from the groupconsisting of an acid, a base and a fluoride compound, and thedeactivation reagent includes a material reactive to polar functionalgroups (e.g., hydroxyl groups) bonded to the sol-gel precursor-formingelement in the coating or to the tube structure.

[0073] The specific steps for fabrication starts with the cleaning andhydrothermal treatment of a fused silica capillary. Then, thepreparation of the sol-gel solution utilizing the above precursors isdone. Next, the inner walls of the hydrothermally treated capillarycolumn are coated with the prepared sol-gel solution. Finally,conditioning of the sol-gel coated capillary tube is performed.

[0074] Referring now to FIG. 2, the selected capillary column 10 isfilled with the prepared sol-gel solution utilizing the device 20 asillustrated in FIG. 2. The device 20 includes a metallic cylindricalpressurization chamber 22 and a bottom cap 24. The bottom cap isremovably attached to a distal end thereof by a screw-threaded portion34. It is understood that any attachment mechanism can be used to securethe bottom cap 24 to the distal portion of the chamber 22. A proximalend of the chamber 22 has a second sealing mechanism 36 with an outletmechanism 26, generally in the form of a cross or any other suitableshape as desired, extending therefrom. This outlet mechanism 26 hasoutwardly extending portions 38, 40, 42 with outlet valves 28, 30contained within the radially extending portions or arms thereof. Theupwardly extending portion of the outlet means 26 has a capillary column10 extending therefrom, which is removably inserted through the upwardlyextending arm of the outlet device.

[0075] As previously mentioned, the sol-gel solution of the presentinvention utilizes various sol-gel precursors. In one embodiment, thesol-gel solution is prepared by mixing two solutions together that areeach prepared in separate polypropylene vials. The first solutioncontains hydroxy-terminated polydimethylsiloxane (PDMS),hydroxy-terminated polydimethyldiphenylsiloxane (PDMDPS),polymethylhydrosiloxane (PMHS) and methylene chloride. The secondsolution is methyltrimethoxysilane, bis(trimethoxysilylethyl)-benzene,1,1,1,3,3,3-hexamethyldisilazane (HMDS) and methylene chloride. Thesetwo solutions are then admixed by vortexing and separated from theensuing precipitate by centrifugation. The supernatant is carefullypipetted out and placed in another vial for insertion into the fillingand purging device. This is accomplished by unscrewing the cap 24,inserting the vial and then replacing the cap 24 to provide an airtightseal. If necessary, Teflon tape or other suitable adhesive mechanism canalso be used in the sealing of the cap 24. In addition, airtight sealingmechanism 44 is in communication with the arm member extending upwardlyfrom the cross-like member and connecting means 46 extending from theradially extending arms.

[0076] Prior to the insertion of the vial 32 into the chamber 22, thevalves 28, 30 are closed and then the capillary column 10 is insertedinto the chamber 22 via the outwardly extending portion of thecross-like member 26 such that it is in contact with the sol-gelsolution contained in vial 32. A gas pressure is selected depending onthe size of the capillary to be filled and this pressure is applied toan inert gas applied to the chamber 22 by opening the valve 28. Thesol-gel is then pushed up from the vial 32 into the capillary 10,completely filling the extent thereof. When the sol-gel solutionoverflows from the distal end of the capillary 10, the inlet valve 28 isclosed and the outlet valve 30 is then opened to release the excesspressure from the chamber 22.

[0077] The solution is allowed to reside inside the full extent of thecapillary column 10 for a desired length of time, according to thethickness of coating to be formed on the inner walls 14 of the tubestructure 12 of the capillary column 10, and the sol-gel reactions takeplace within the capillary column 10. These reactions include chemicalbonding of the inner walls 14 of the tube structure 12 with thecomponents of the sol-gel by virtue of the silanol groups in thepolymeric network reacting with the silanol groups of the silica tubestructure 12. This reaction forms an immobilized sol-gel surface coatingintegral with the inner walls 14 of the tube structure 12. The nowfilled capillary is then subjected to further processing.

[0078] After the reaction period for the sol-gel solution is completed,the outlet valve 30 is closed and the inlet valve 28 is opened to allowfor an inert pressurized gas to be again introduced into the capillary10. Prior to this gas introduction, the cap 24 is opened to remove thevial 32, leaving the chamber 22 without any members other than thedistal end of capillary 10 extending thereto. This gas purging allowsthe excess sol-gel solution, which has not yet bonded to the capillarywalls to be purged from the capillary 10 via its distal end. Purgingwith the inert gas also removes any residual solvent or other volatilesfrom the capillary 10.

[0079] Final conditioning of the capillary 12 is accomplished by sealingthe ends of the capillary after it is removed from the device 20 by useof any known sealing means such as an oxy-acetylene torch. A programmedsystem of heating is then applied to the capillary and then the sealsare removed to allow for solvent rinsing after which a final programmedtemperature drying with simultaneous inert gas purging is performed. Thecolumn thus prepared is ready then for use.

[0080] The above discussion provides a factual basis for the use of thecolumn and related method described herein. The methods used with autility of the present invention can be shown by the followingnon-limiting examples and accompanying figures.

EXAMPLES

[0081] The following examples specifically provide for the specificmethods and materials utilized with the present invention.

[0082] Materials:

[0083] Fused silica capillary (250 μm i.d.) can be obtained fromPolymicro Technologies Inc. (Phoenix, Ariz., USA). HPLC-Gradetetrahydrofuran (THF), methylene chloride, and methanol were purchasedfrom Fisher Scientific (Pittsburgh, Pa., USA). Tetramethoxysilane (TMOS,99+%), poly(methylhydrosiloxane) (PMHS), and trifluoroacetic acid(containing 5% water), were purchased from Aldrich (Milwaukee, Wis.,USA) Hydroxy-terminated poly(dimethylsiloxane) (PDMS),methyl-trimethoxysilane (MTMS) and trimethylmethoxysilane (TMMS) werepurchased from United Chemical Technologies, Inc. (Bristol, Pa., USA).Ucon 75-H-90,000 polymer was obtained from Alltech (Deerfield, Ill.,USA).

[0084] Gas chromatographic experiments have been carried out on aShimadzu Model 14A capillary GC system. A Jeol Model JSM-35 scanningelectron microscope has been used for the investigation of coatedsurfaces. A homemade capillary filling device has been used for fillingthe capillary with the coating sol solution using nitrogen pressure. AMicrocentaur Model APO 5760 centrifuge has been used to separate the solsolution from the precipitate. A Fisher Model G-560 Vortex Genie 2system has been used for thorough mixing of various solutioningredients. A Barnstead Model 04741 Nanopure deionized water system wasused to obtain 17.8 MΩ water.

Example One

[0085] The inner surface of an appropriate length of a fused silicacapillary is cleaned by sequentially rinsing with 5 ml each of thefollowing solvents:

[0086] (a) methylene chloride;

[0087] (b) methanol; and

[0088] (c) deionized water.

[0089] The capillary is then purged with a flow of helium, or any otherinert gas, for 5 minutes leaving behind a thin coating of deionizedwater on the inner surface of the capillary. The two ends of thecapillary are then sealed with an oxy-acetylene flame. The sealedcapillary was then heated by programming the temperatures from aninitial value of 40° C. to a final value of 300° C. at a rate of changeof 4° C. per minute, and allowing the thermal treatment at the finaltemperature to continue for approximately 120 minutes. The capillary wasallowed to cool down to room temperature, and then the ends are cutopen. The capillary was then purged again with an inert gas, the flowrate being 1 ml per minute while being simultaneously heated at the sameprogrammed temperature as delineated before.

[0090] Two solutions were then prepared in separate polypropylene vials:(1) Solution 1: (a) Hydroxy-terminated Polydimethylsiloxane (PDMS) 0.025g (b) Hydroxy-terminated Polydimethyldiphenylsiloxane 0.025 g (PDMDPS)(c) Polymethylhydrosiloxane (PMHS) 25 μl (d) Methylene chloride 600 μl(2) Solution 2: (a) Methylteimethoxysilane (MTMS) 5 μl (b)bis(trimethoxysilylethyl)-benzene 10 μl (c)1,1,1,3,3,3-hexamethyldisilazane (HMDS) 10 μl (d) methylene chloride 280μl

[0091] The solutions were then mixed together by thorough vortexing.This was followed by the addition of 50 μl of trifluoroacetic acid(containing 5% water) and vortexed again. Further, a 20 μl volume of amethanolic solution of ammonium fluoride (20 mg/ml) was added to themixture. The precipitate was separated out by centrifugation and thesupernatant was carefully pipetted out and transferred to a clean vial.This final sol-gel solution was then further used to coat the capillarycolumn.

[0092] The pre-treated capillary tube was then filled with the sol-gelsolution and allowed to sit for a selected residence time (e.g. 10-30minutes). This allowed the sol-gel polymer to be formed in the solsolution and get bonded to the inner walls of the capillary. The excess,unreacted sol-gel solution was then expelled from the capillary underhelium or other inert gas pressure, leaving the surface-bonded coatingon the inner surface of the capillary tube. Volatiles and residualsolvents or sol-gel solution were then purged off the tube using heliumor other inert gas for 30-60 minutes.

[0093] Both ends of the now coated and gas-filled capillary were sealedand then heated by use of a programmed temperature sequence. Thissequence was as follows, but other modifications of this are within thescope of the present invention:

[0094] (1) Heating from 40° C. to 150° C. at 1° C. per minute with anincremental change with a hold time of 5 hours at 150° C.

[0095] (2) Heating the column from 150° C. at programmed sequentialincrements to a final temperature of 350° C. or any other temperaturesuitable for the selected sol-gel matrix. This heating was allowed tocontinue for a hold time of approximately 60 minutes.

[0096] (3) Opening of the ends of the column.

[0097] (4) Rinsing of the column with a selected solvent mixture, e.g.1:1 v/v methylene chloride/methanol mixture.

[0098] (5) Drying of the coated capillary under helium purge and furthertemperature programming conditions; e. g., 40° C. to 350° C. at 6° C.per minute.

[0099] The column was then ready for use in chromatographic analysis. Inorder to test the efficacy of the columns of the present invention,several columns were prepared with and without the preferred reagents ofthe present invention.

Example Two

[0100] Preparation of Columns With and Without Ammonium FluorideSolution 1 (for column without ammonium fluoride): PDMS 0.025 gPolydimethyldiphenylsiloxane in 200 μl methyl chloride 0.025 g PMHS 25μl Methyl chloride 400 μl Solution 2 (for column without ammoniumfluoride): M-TMOS 5 μl BIS 10 μl HMDS 10 μl Methylene chloride 310 μl

[0101] As before, the two solutions were combined and introduced into afused silica capillary tube and post-treated according to the methodabove. A GROB test mixture was then run. Solution 3 (for column withammonium fluoride): PDMS 0.025 g Polydimethyldiphenylsiloxane in 200 μlmethylene chloride 0.025 g PMHS 25 μl Methylene chloride 400 μl Solution4 (for column with ammonium fluoride): M-TMOS 5 μl BIS 10 μl. HMDS 10 μlMethylene chloride 310 μl

[0102] Again, solutions 3 and 4 were mixed together, however, inaddition 50 μl TFA (5% water), 20 μl of methanolic ammonium fluoridewere added after the initial mixing and centrifuging. Another testsolution was run on this column after the final treatment steps.

[0103] Results of comparison studies of columns prepared without andwith the ammonium fluoride are illustrated in FIGS. 3A and 3B.

Example Three

[0104] Preparation of Columns With and Without BIS Solution 1 (withBIS): PDMS 0.025 g Polydimethyldiphenylsiloxane with 0.025 g 200 μlmethylene chloride PMHS 25 μl Methylene chloride 400 μl Solution 2 (withBIS): M-TMOS 5 μl BIS 10 μl HMDS 5 μl Methylene chloride 285 μl

[0105] The vials were admixed as above and after centrifuging for 10minutes, the ammonium fluoride catalyst is added to the mixture. Thecolumn was prepared by the method presented before. Solution 3 (withoutBIS): PDMS 0.025 g Polydimethyldiphenylsiloxane in 0.025 g 200 μlmethylene chloride PMHS 25 μl Methylene chloride 400 μl Solution 4(without BIS): M-TMOS 5 μl HMDS 5 μl Methylene chloride 285 μl

[0106] As above, the columns was prepared according to the procedureoutlined before.

[0107] Both columns were tested using a GROB test mixture and theresulting spectra are shown in FIGS. 4A and 4B. The column with the BIScomponent clearly shows improved baseline stability and better peakresolution.

Example Four

[0108] Columns Prepared With and Without HMDS Solution 1 (with HMDS):PDMS 0.025 g Polydimethyldiphenylsiloxane in 0.025 g 200 μl methylenechloride PMHS 25 μl Methylene chloride 400 μl Solution 2 (with HMDS):M-TMOS 5 μl BIS 10 μl HMDS 5 μl Methylene chloride 285 μl Solution 3(without HMDS): PDMS 0.025 g Polydimethyldiphenylsiloxane in 0.025 g 200μl of methylene chloride PMHS 25 μl Methylene chloride 400 μl Solution 4(without HMDS): M-TMOS 5 μl BIS 10 μl Methylene chloride 290 μl

[0109] The columns were again prepared by the methods already disclosed,including the addition of the ammonium fluoride catalyst step. Theresults of the spectra of GROB test solution runs are shown in FIGS. 5Aand 5B. Again, the addition of the HMDS gave improved results.

Example Five

[0110] Optimized Solution Solution 1: PDMS 0.025 gPolydimethyldiphenylsiloxane in 0.025 g 300 μl methylene chloride PMHS25 μl Methylene chloride 300 μl Solution 2: M-TMOS 5 μl BIS 10 μl HMDS10 μl Methylene chloride 280 μl

[0111] The columns were prepared according to the already disclosedmethod.

[0112] As can be seen from the above examples and Table 1, the columnsof the instant invention demonstrated a reproducibility in results bothrun-to-run and column-to-column.

[0113] Throughout this application, various publications, includingUnited States patents, are referenced by author and year and by patentnumber. Full citations for the publications are listed below. Thedisclosures of these publications and patents in their entireties arehereby incorporated by reference into this application in order todescribe more fully the state of the art to which this inventionpertains.

[0114] The invention has been described in an illustrative manner, andit is to be understood that the terminology used is intended to be inthe nature of words of description rather than of limitation.

[0115] Obviously, many modifications and variations of the presentinvention are possible in light of the above teachings. It is,therefore, to be understood that within the scope of the appendedclaims, the invention can be practiced otherwise than as specificallydescribed. TABLE 1 Retention Time and Retention Factor ReproducibilityData Obtained on three Sol-Gel Coated PEG colum in 5 Replicate Runs PeakRSD RSD # NAME tr SD % k SD % COLUMN NUMBER 1 1 n-Hexadecane 2.38 0.020.71 3.4 0.03 0.94 2 Methyl Undecanoate 4.48 0.09 1.96 7.37 0.10 1.34 31-Decanol 2.79 0.00 0.14 3.72 0.01 0.24 4 n-Octadecane 3.63 0.05 1.385.72 0.09 1.63 5 2,6-Dimethylphenol 3.15 0.02 0.67 4.8 0.04 0.92 62-Ethylhexanoic acid 6.1 0.14 2.21 10.3 0.25 2.42 7 Hexanophenone 10.120.13 1.30 17.75 0.24 1.37 8 Eicosane 18.43 0.41 2.25 33.13 0.76 2.29COLUMN NUMBER 2 1 n-Hexadecane 1.93 0.01 0.31 2.26 0.01 0.40 2 MethylUndecanoate 2.49 0.00 0.16 3.22 0.00 0.12 3 Dicyclohexylamine 2.64 0.031.14 3.48 0.06 1.72 4 1-Decanol 2.79 0.00 0.14 3.72 0.01 0.24 5n-Octadecane 3.81 0.00 0.10 5.45 0.01 0.15 6 2,6-Dimethylphenol 4.220.00 0.09 6.15 0.00 0.07 7 2-Ethylhexanoic acid 4.87 0.00 0.08 7.25 0.010.11 8 Hexanophenone 6.94 0.01 0.12 10.70 0.00 0.00 9 Eicosane 8.23 0.010.12 12.92 0.02 0.15 COLUMN NUMBER 3 1 n-Hexadecane 1.50 0.01 0.80 1.550.02 1.35 2 Methyl Undecanoate 1.72 0.01 0.70 1.92 0.02 1.09 3Dicyclohexylamine 1.78 0.01 0.56 2.01 0.02 0.75 4 1-Decanol 2.29 0.062.53 2.89 0.10 3.49 5 n-Octadecane 2.56 0.00 0.00 3.33 0.00 0.00 62,6-Dimethylphenol 2.86 0.01 0.42 3.84 0.02 0.52 7 2-Ethylhexanoic acid3.84 0.02 0.44 5.50 0.03 0.51 8 Hexanophenone 4.53 0.02 0.33 6.67 0.030.39 9 Eicosane 6.01 0.05 0.83 9.18 0.09 0.94

References

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What is claimed is:
 1. A capillary column comprising: a tube structureincluding inner walls; and a sol-gel substrate coated on a portion ofsaid inner walls of said tube structure to form a stationary phasecoating on said inner walls, said sol-gel substrate including at leastone baseline stabilizing reagent residual and at least one surfacedeactivation reagent residual.
 2. The capillary column according toclaim 1, wherein said at least one baseline stabilizing reagent residualis selected from the group consisting of residuals frombis(trimethoxysilylethyl)-benzene, sol-gel active reagents withphenyl-containing groups, and cyclohexane-containing groups.
 3. Thecapillary column according to claim 1, wherein said at least one surfacedeactivation reagent residual is selected from the group consisting of1,1,1,3,3,3-hexamethyldisilazane, hydrosiloxane, and hydrosilane.
 4. Thecapillary column according to claim 1, wherein said sol-gel substrate ismade from sol-gel precursors having the general structure:

wherein, Z=a precursor-forming element selected from the groupconsisting of silicon, aluminum, titanium, zirconium, vanadium, andgermanium, alkyl moieties and their derivatives, alkenyl moieties andtheir derivatives, aryl moieties and their derivatives, arylene moietiesand their derivatives, cyanoalkyl moieties and their derivatives,fluoroalkyl moieties and their derivatives, phenyl moieties and theirderivatives, cyanophenyl moieties and their derivatives, biphenyl moietyand its derivatives, cyanobiphenyl moieties and their derivatives,dicyanobiphenyl moieties and their derivatives, cyclodextrin moietiesand their derivatives, crown ether moieties and their derivatives,cryptand moieties and their derivatives, calixarene moieties and theirderivatives, liquid crystal moieties and their derivatives, dendrimermoieties and their derivatives, cyclophane moieties and theirderivatives, chiral moieties, and polymeric moieties; and R₁, R₂, R₃,and R₄=R-groups that are moieties selected from the group consisting ofsol-gel-active moieties, alkoxy moieties, hydroxy moieties,non-sol-gel-active moieties, methyl, octadecyl, and phenyl.
 5. Thecapillary column according to claim 4, wherein said alkoxy groups areselected from the group consisting of a methoxy group, ethoxy group,n-Propoxy group, iso-Propoxy group, n-butoxy group, iso-butoxy group,and tert-butoxy group.
 6. The capillary column according to claim 4,wherein said R-groups are at least two moieties selected from the groupconsisting of sol-gel active moieties, alkoxy moieties, and hydroxymoieties.
 7. The capillary column according to claim 6, whereinremaining said R-groups are moieties selected from the group consistingof methyl, octadecyl, phenyl, and hydrogen.
 8. The capillary columnaccording to claim 1, wherein said sol-gel substrate further includes aresidual deactivation reagent selected from the group consisting ofpolymethylhydrosiloxane and hexamethyldisilazane.
 9. The capillarycolumn according to claim 1, wherein said tube structure is made ofmaterials selected from the group consisting of glass, fused silica,alumina, titania, and zirconia.
 10. A method of making a sol-gelcapillary solution for placement into a capillary column by: mixingsuitable sol-gel precursors to form a sol-gel solution; stabilizing thesol-gel coating by adding at least one baseline stabilization reagent tothe sol-gel solution; deactivating the sol-gel coating by adding atleast one surface deactivation reagent to the sol-gel solution; andreacting the solution in the presence of at least one catalyst.
 11. Themethod according to claim 10, wherein said reacting step furtherincludes adding trifluoroacetic acid as the catalyst and the additionalcatalyst is selected from the group consisting of acids, bases orfluorides.
 12. The method according to claim 10, including the step ofadding ammonium fluoride as an additional catalyst.
 13. The methodaccording to claim 10, including the step of hydrothermally pre-treatingthe capillary column.